This invention relates to consumable welding wires and more particularly to a composite welding wire having an alloy core.
With the increasing utilization of a wide variety of metals and numerous alloys thereof, there has been a corresponding increase in the demand for welding wires which are suitably "matched" with the materials to be welded. Thus, a single welding wire having a predetermined composition cannot generally provide a satisfactory weld for all of the various alloys of the base metal. However, it is often not only difficult and expensive to manufacture a number of alloy welding wires which are particularly "matched" with the alloys of the base metal, but long manufacturing or lead times are also required.
To overcome these drawbacks, composite or cored welding wires have been developed which essentially comprise a powdered core portion with a casing or tubular portion enclosing the core material. As exemplified by U.S. Pat. Nos. 2,785,285; 3,418,446; 3,513,287 and 3,834,002 a variety of methods may be utilized to form a composite welding wire. For example, as more particularly disclosed in U.S. Pat. No. 3,418,446, a welding wire may be made by folding an elongated strip of flat metal into a channel shape with a powdered core material added thereto. Subsequently, the strip is folded and formed to encompass the core material with a lap or butt joint being formed between the edges of the strip. Once the strip has been formed, the electrode is drawn to achieve the desired diameter. Problems associated with the formation of composite welding wires, such as the localized collapse of the casing due to irregular compaction of the core material, reaction of the core material with impurities and atmospheric elements and work hardening of the casing material, have been corrected by uniformly compacting the core material and annealing the casing during the forming operations.